Table i



iilib ji United States Patent 3,030,217 REFRACTORY RAMMING COMPOSITION Lewis W. Chantler and William O. Hund, Charles Town,

W. Va., assignors, by mesne assignments, to Martin- Marietta Corporation, Chicago, 11]., a corporation of Maryland No Drawing. Filed Nov. 4, 1958, Ser. No. 771,751

19 Claims. (Cl. 106-59) This invention relates to refractory composition. More particularly, it relates to magnesia, magnesia-chrome and chrome-magnesia refractories and to the bonding of the materials in a refractory body. Still more particularly, it relates to refractory composition for use in constructing and patching of industrial furnace parts such as for example, open hearth furnace bottoms, converter linings, and the like.

With the development of newer metallurgical processes and the demand for better refractories for existing processes there is a need for refractory materials and ramming mixes which are capable of withstanding the more severe operating conditions. For satisfactory service, it is desirable that the combination of refractory material and bonding material develop adequate refractory characteristics, possess resistance to chemical action under heat and resistance to thermal shock so as to approach the characteristics of the magnesia, magnesia-chrome or chrome-magnesia refractory which it binds into a solid structure.

Magnesia compositions, useful as ramming mixes, have been produced by chemically bonding the refractory. These chemically bonded refractories or ramming mixes, generally have consisted of sized magnesia or magnesium material with a water soluble or water plasticized material as binder. For example, sodium silicate imparts to ramming mixes too great shrinkage and failure after firing to present continuous impermeable base. Sodium silicate promotes hydration of the magnesia causing expansion. Further, the density of mixes containing sodium silicate have been acceptable in the absence of higher density products of equivalent good properties of nonshrinkage, hydration, etc. Others of ,the known chemically bonded refractories undergo considerable change in volume, usually shrinkage, during firing which shrinkage gives rise to cracks permitting molten metal to penetrate or strike through the lining, so weaken-ing the refractory that the load bearing characteristics thereof are materially diminished. Shrinkage cracks may also occur during firing due to the swelling of the magnesia composition through hydration during the mixing and subsequent stages of handling prior to firing.

To be useful, the ramming mixes must meet certain minimum requirements for, among other properties, strength, density, shrinkage and hydration. Sodium silicate has been one of the chemicals used in ramming mixes as a bonding agent for magnesium compounds. Sodium silicate imparts excellent strength to such compositions. It has the disadvantages of promoting hydration, adding an undesirable component, silicon dioxide and increasing shrinkage upon burning. Other chemicals such as fillcarinacsmnounds harshest! ad ed o e r mincreasethe strength thereof. Chrome ore may beifsed iii these compositions in quantities introducing up to about 3% of the mix calculated on a Cr O basis. Boron compounds have also been incorporated in the ramming mixes to minimize swelling due to hydration and cracking during firing. These mixes may comprise from 0.25% to 5% of the boron compound calculated as 2 3- Organic acids have also been used in magnesia or magnesia-oxy cements. These acids were introduced ice into magnesia cement compositions containing reactive magnesia, with or without added salts such as magnesium sulphate, lime, and the like. Any organic acids, liquid or solid, such as acetic acid, citric acid, salicyclic acid, etc. are useful reactants in these compositions containing reactable magnesium components. These organic acidreactive magnesia or magnesia plus reactive magnesium salt cements will crack during firing and will not meet the strength and other requirements for refractories in modern metallurgical processes.

Broad-1y stated, the present invention contemplates a mixture of several ingredients wherein unusual properties for the desired purpose are attributable to the mixed or combined relationship of the ingredients and to the method of producing a refractory from said mixture or ingredients. The improved refractory material comprises dead-burned magnesite and a salt component selected from the group consisting of alkali metal salts of monohydroxy aromatic monocarboxylic acid and mixtures thereof. In adapting the refractory material to specific use, the refractory may coritain'falchromium bearing material either-of mm refractory type or chromiInn-bindermat'rials andil'sb 'sma-ll amounts of sodium silicate, for example, 1 to,,5% by weigh'tTf","""

Chromiu binder in erials are to be distinguished from chrome oFes WElCl'l are mixtures of chromium, aluminum, iron, and the like, complexes of oxides, silicates, etc. As binder, chromium compounds are used in quantities generally less than 3% by weight of the mix on a Cr O basis. Chrome ore on the other hand may constitute up to 50% or even more of the refractory mix.

The magnesia which is employed can be any high purity dead-burned magnesite obtained by calcining high grade natural ores such as m agnesite or brucite, or it can be obtained by calcining any magnesium compound which yields magnesium oxide upon calcination. The magnesia can be obtained, for instance, by recovering magnesium chloride from potash solutions and heating the magnesium chloride under conditions to evolve hydrochloric acid and produce magnesium oxide. This MgO product, with or without compounding with materials such as talc, is calcined to produce dead-burned magnesia of 93% or higher purity. The magnesia also can be produced by calcining relatively pure magnesium hydroxide or magnesium carbonate at temperatures usually ranging from 2700- 3500 F.

The ma nesite is employed in the dead-burned state. Chemical analysis of typical magnesias shows various components in the following ranges.

Material: .Ranges, percent Si0 2.5-8 F203 1.04 A1 0 0.5-3 CaO 1.5-6 MgO -95 Screen sizlngs (1) (2) (3) (4) Percent pass 34 100 100 #4 94 97 #3.-. 64 76 99 100 #lfi.-. 51 56 81 #30.-. 49 41 56 65 23 32 27 Such products may be made by screening out various 3,030,217 Patented Apr. 17, 1962 groups of particles sizes and then recombining them to obtain the desired particle size curve. As many as four or five diiferent sized products may be recombined to form a ramming mix. It is usually preferable to maintain a content of 20% to 40% of material passing a #100 mesh screen. These sizings, shown as applicable to magnesia, may also be applied to chrome ore if that is a desired component of the ramming mix.

A typical chrome ore useful for the purposes of this When preparing ramming mixes containing chu'ome ore, the basic constituents, i.e., the mixture of magnesia and chrome ore generally have a chemical analysis falling in the following ranges.

Percent SiO, 3.0-8

Feaoa a e a MgO 40-80 To the basic ramming mix constituents is added alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon wherein R represents a radical selected from the group consisting of hydrogen, methyl, ethyl and ethyl radicals substituted with halogen, oxygen, nitro, etc., groups and n is an integer from 0 to 4.

Salts of these acids are mixed with refractory composition components in quantities varying from 0.25% to 2.5% by weight. Useful alkali metal salts are the sodium, potassium, lithium, etc., salts. Representative acids are ortho, meta and pyro hydroxy benzoic acids such as salicylic acid, monobasic phenolic acids having the carboxyl on the side chain as o-hydroxy-phenyl-acetic acid, p-hydroxy-phenyl-propionic acid, and the like.

Chrome ore is useful in this invention in quantities up to 70% of the dry mix. Chromium compounds, useful as binders are, for example, chromic acid, chromiumcontaining salts, chromous sulphate, chromic sulphate, chromic halides, chromic oxalate, chromates and dichromates. Chromium salts or acids acting as binders, calculated as Cr O may constitute up to 3% by weight of the dry mix.

In preparing the ramming mix compositions according to the present invention, the components can be mixed together and water added for immediate use or the dry mixture can be stored or shipped. It is preferred to grind each component separately and mix the ground materials. If desired, when the ramming mixes are to contain chromium, the magnesia component and the chromium component can be ground together.

When the dry ramming mix has been thoroughly mixed with 3-6 lbs. of water per 100 lbs. of dry ramming mix composition to form a wetted mixture, the material can be formed by ramming in any manner known to the art. When making up the batches, the particle size of the components can, if desired, be selected in order to provide dense packing in the known manner.

When utilizing a ramming mix for the preparation of furnace linings, a representative ramming mix, prepared from comminuted periclase, showed a particle size 39% of which passed through a 100 mesh U.S. standard screen. This dead-burned magnesite possessed a particle size as follows:

96% passing a No. 4 U.S. standard screen; 64% passing a No. 8 U.S. standard screen; 49% passing a No. 30 U.S. standard screen.

This magnesite material showed a chemical analysis of:

=In order to obtain the proper forming characteristics, solids are wetted with varying amounts of water depending upon the mode of application and upon the area of application. In general, mixes may carry between about 3 and about 10% of water. Ramming mixes usually are limited to between about 3% and about 6% but under special conditions amounts outside of this range may be utilized. For gunning of this type of refractory mixture, higher water content is initially introduced in order to be certain that the deposited mixture has suitable characteristics at the time of deposition by which time some of the initially incorporated water has been evaporated.

When the above specified mixture is mixed with 4 parts of water per 100 parts by weight of dry ramming mix composition, this ramming mix will be transferred into place for firing and the mix will hold its shape and can be fired by bringing up to a temperature of approximately 2800-2900 F. over a period of about 72 hours.

For comparative tests, results of which are summarized in Table I, refractory materials were prepared as follows:

To form a batch A, there was admixed a magnesia mix of the following composition by size:

100% passing 4 inch screen 94% passing #4 screen 64% passing #8 screen 51% passing #16 screen 34% passing #100 screen and 2% of powdered sodium salicylate. The ingredients were thoroughly blended dry in a revolving-blade type mixer and approximately 4% of water added to produce a uniformly wetted composition. This composition was rammed into Dietert cylinders of 2 inch diameter utilizing a 14 lb. weight. After the mold was removed, the cylinders were dried for 16 to 24 hours at 220 F. The second set of cylinders were dried for 16 to 24 hours at 220 F. and then fired at 2910" F. for two hours.

Weight and dimension of dried cylinders were obtained before and after burning, so as to determine shrinkage. Hydration was determined on rammed and dried cylinders by autoclaving the dried cylinders at p.s.i.g. for 3 hours. The resulting material was dried by heating to 220 F. while circulating dry air and screened on a #30 U.S. standard screen.

Crushing strength of dried but unfired cylinders was obtained by crushing in a hydraulic press.

The following tables show a comparison of ramming mixes prepared from identical magnesite base but utilizing sodium salicylate and sodium silicate as salicylic acid binders.

TABLE I P t hi 2910 F., 2 his.

ercen 1115 ng A mixture Perramming Dry, strength,

cent water ib./cu. it. p.s.l. Percent Percent Percent wt. loss vol. height shrink. shrink.

Sodium Sallcylute... 2 4 167 4,700 2.6 1.1 .9 Sodium Sihcote 4 4 157 4,030 3. 8 13. 4 4.3 Salicylic Acid 2 4 156 1,080 3.2 9.8 2.8

TABLE 11 form by tumbling in a revolving drum mixer. At the time of use, the composition is wetted by adding 4% P r v D G n A by weight of water. The wetted material was rammed Admmm ceent 5 "fig 333" into position where it set to a dense compacted mass. e t cree After firing for about 48 hours to a temperature of about 2910 F., the mass set to a hard refractory mass. Sodium Sallcylate 2 90. 9 89.9 fair-good. Sodium Silicate 4 84.9 64.2 poor. Example H Salicylic Acid 2 91.4 91.6 good. 20

A refractory sultable fornpatch ng a furnace lining was Dietcrt cylinders of the above admixtures utilizing an alkali metal salt of an acid such as salicylic acid as binder, when dried, show increased density as compared to magnesia ramming mixes containing sodium silicate. These cylinders, fired at 2910 F. for two hours, also show considerably lower shrinkage than like cylinders using sodium silicate as a binder. These mixes show negligible hydration whereas the cylinders utilizing sodium silicate as a binder show appreciable hydration.

This superiority of the salts of hydroxy aromatic carboxylic acids is unexpected because for use with reactive magnesias salicylic acid and the salts thereof are equivalents but for use in ramming mixes prepared from deadburned magnesites the fired refractories prepared using salicylic acid exhibit low density and poor strength compared to the salts thereof.

To illustrate the superiority of the magnesia ramming mixes prepared with alkali metal salts of hydroxy aromatic carboxylic acids comparison is set forth showing improved density, improved crushed strength and lower shrinkage as compared to sodium silicate, the most commonly used binder agent.

TABLE HI Oven Percent Oven dried burnt Binder Percent dried crushing volume density strength, shrinkage Sodium Silicate 4 157 4, 030 12.2 Sodium Salicylate 2 168 4, 700 7. 1

The following examples will illustrate more clearly the ramming mix composition, method of preparation thereof and refractory compositions resulting from the firing of said compositions.

Example I was crushed and a mixture of particles prepared which showed 60% passing a #8 U.S. standard screen and retained on a #30 U.S. standard screen and 30% passing the #100 U.S. standard screen. To each 99 parts of this magnesia material was added one part by weight of powdered sodium salicylate and the composition rendered uniprepared froiif'thd magnesite whose chemical analysis is given in Example I. 45 parts by weight of particles of this magnesite of a size passing a inch U.S. standard screen and retained on a #8 U. S. standard screen, 26 parts of magnesite of a size passing a #8 U.S. standard screen and retained on a #100 U.S. standard screen and 27 parts of magnesite of a size passing a #100 U.S. standard screen were mixed with two parts by weight of powdered sodium salicylate and the composition rendered uniform by tumbling in a revolving drum mixer.

Wetted material was formed into shaped masses where it set to a dense compacted mass. After firing for about 72 hours at a temperature of about 2910 F., the shaped masses set to a hard refractory mass.

Example III A refractory suitable for patching a furnace lining was prepared from the magnesite whose chemical analysis is given in Example I.

50 parts by weight of particles of magnesite of a size passing a inch U.S. standard screen and retained on a #8 US. standard screen was mixed with 49 parts by weight of chrome ore of the analysis shown hereinbefore when discussing chrome ore, having a particle size such that 100% passed a #30 U.S. standard screen.

To 99 parts by weight of the dry mixture was added 1 part by weight of powdered sodium salicylate from the same source as the sodium salicylate utilized in Example I.

The mixture was agitated and rendered uniform by tumbling in a revolving drum mixer. At the time of use, the composition is wetted by adding 4% by weight of water. The mixture was rammed into shape. After firing for about 48 hours at a temperature of about 2910" F., the rammed material set to a hard mass exhibiting substantially no shrinkage or cracking.

Example IV A refractory suitable for patching a furnace lining was prepared from the magnesite whose chemical analysis is given in Example I.

50 parts by weight of particles of magnesite of a size passing a A'inch U.S. standard screen and retained on a #8 U.S. standard screen and 47 parts by weight of magnesite of a particle size passing a #30 U.S. standard screen were agitated to obtain a uniform mixture.

To each 97 parts by weight of this mixture of magnesia particles was added 2 parts of sodium silicate powder of a particle size 100% passing a #30 screen and passing a U.S. standard screen and 1 part by weight of powdered sodium salicylate. This composition was agitated and the composition rendered uniform by tumbling in a revolving drum mixer. At the time of use, the composition is wetted by adding 4% by weight of water.

tached to the aromatic nucleus and the carboxylgroup is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms.

2. A refractory ramming mixture consisting essentially of dead-burned magnesite and between about 0.25 and about 2.5% of alkali metal salt of an acid having the general formula nC O OH wherein R represents a radical selected from the group consisting of hydrogen, methyl, ethyl and substituted ethyl radicals and n is an integer from to 4.

3. A refractory ramming mixture consisting essentially of dead-burned magnesite and between about 0.25 and about 2.5% of alkali metal salt of hydroxy benzoic acid.

4. The refractory ramming mixture of claim 3 wherein the salt is sodium salicylate.

5. A refractory ramming mixture consisting essentially of dead-burned magnesite and between about 0.25% and about 2.5 of alkali metal salt of mono basic phenolic acids having the carboxyl group on a hydrocarbon side chain having a maximum length of four carbon atoms.

6. The method of preparing refractory compositions which comprises admixing dead-burned magnesite, between about 0.25 and about 2.5% of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms, adding water to said admixture to produce a mixture of wetted particles, ramming the wetted mixture of particles into position, hardening the wetted mixture and firing.

7. The method of preparing refractory compositions which comprisesadmixing dead-burned magnesite, 0.25 and about 2.5% 'of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the hydroxy is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms, adding between about 3% and about of water to said admixture to produce a mixture of wetted particles, forcing the wetted mixture of particles into position, hardening the wetted mixture and firing the positioned mixture.

8. The method of preparing refractory compositions which comprises admixing dead-burned magnesite, between about 0.25% and about 2.5 of alkali metal salt of an acid having the general formula wherein R represents a radical selected from the group burned magnesite, between about 5% and about 40% by weight of the dry mixture of chrome ore, the ore being calculated as Cr O between about 0.25% and about 2.5 of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms, adding water to said mixture to produce a mixture of wetted particles, ramming the wetted mixture into position, hardening the wetted mixture by drying and firing.

10. A method of making a refractory furnace lining using ramming mix which comprises admixing deadburned magnesite, up to 3% by weight of chromium salt calculated as Cr O between about 0.25% and about 2.5% of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms, adding water to said admixture, to produce a mixture of wetted particles, ramming the wetted mixture into position, hardening the wetted mixture by drying and firing.

11. A method for making a refractory furnace lining using ramming mix which comprises admixing deadburned magnesite, between about 1% and about 5% by weight of sodium silicate and between about 0.25 and about 2.5% of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group'is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms, adding water to said admixture to produce a mixture of wetted particles, ramming the wetted mixture into position, hardening the wetted mixture by drying and firing.

12. A refractory ramming mixture which consists essentially of dead-burned magnesite, up to about 70% by weight of the dry mixture of chrome ore and between about 0.25% and about 2.5% by weight of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms.

13. A refractory ramming mixture which consists essentially of dead-burned magnesite, up to 3% by weight of chromium salt, calculated as Cr O and between about 0.25% and about 2.5% by weight of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms.

14. A refractory ramming mixture which consists essentially of dead-burned magnesite, between about 1% and about 5% by weight of sodium silicate and between about 0.25% and about 2.5% by weight of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxyl group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms.

15. A refractory ramming mix which consists essentially of dead-burned magnesite of a particle size such that will pass through a inch U.S. standard screen and about 23% will pass through a #100 US. standard screen, and between about 0.25% and about 2.5% of alkali metal salt of monohydroxy aromatic monocarboxylic acid in which the hydroxy group is attached to the aromatic nucleus and the carboxyl group is at most removed from the aromatic nucleus by an aliphatic chain of four carbon atoms.

16. A refractory ramming mix which consists essentially of dead-burned magnesite of a particle size such that 69 parts by weight pass a #8 US. standard screen and 9 is retained on a #30 U.S. standard screen and 30 parts by weight pass the #100 U.S. standard screen, one part by weight per each 99 parts of magnesium material of powdered sodium salicylate and 4 parts of water per 100 parts of solids.

17. A refractory ramming mix which consists essentially of dead-burned magnesia, said magnesia being of a particle size such that 45 parts by weight pass 21 Ms inch U.S. standard screen and are retained on a #8 U.S. standard screen, 26 pafts by weight pass a #8 U.S. standard screen and are retained on a #30 U.S. standard screen and 27 parts by weight pass a #100 U.S. standard screen, two parts by weight of sodium salicylate and four parts by weight of water per 100 parts by weight of dry solids.

18. A refractory ramming mix which consists essentially of dead-burning magnesite of a particle size such that 50 parts by weight passes a #8 U.S. standard screen and is retained on a #30 U.S. standard screen and 49 parts by weight of chrome ore 100% of which passes a #30 U.S. standard screen, one part by weight of powdered sodium salicylate per each 99 parts of magnesium material and 4 parts of water per 100 parts of solids.

19. A refractory ramming mix which consists essential- 1y of dead-burning magnesite of a particle size such that 50 parts by weight passes a Vs inch U.S. standard screen References Cited in the file of this patent UNITED STATES PATENTS 2,501,336 Hyde Mar. 21, 1950 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa tent No. 3,030 2l7 April 17 1962 Lewis W. Chantler eta1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3 line 54, after "chain" insert such co1umn 5 after TABLE I insert as a new paragraph "Upon hydratlon of mixes results were as follows; -g line 71 for "60%" read 69% column 8 line 9 for "mixture" first. occurrence read admixture column 9 line 17 and column 10, line 7 for "dead-burning" each occurrence read dead-burned ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A REFACTORY RAMMING MIXTURE CONSISTING ESSENTIALLY OD DEAD-BURNED MAGNESITE AND BETWEEN ABOUT 0.2K% AND ABOUT 2.5% OF ALKALI METAL SALT OF MONOHYDROXY AROMATIC MONOCARBOXYLIC ACID IN WHICH THE HYDROXYL GROUP IS ATTACHED TO THE AROMATIC NUCLEUS AND THE CARBOXYL GROUP IS AT MOST REMOVED FROM TH AROMATIC NUCLEUS BY AN ALIPHATIC CHAIN OF FOUR CARBON ATOMS. 